These are just questions so I strongly suggest you not do anything unless you know what you're doing:

- You were trying to format the drive: can I assume you have a recovery console? If you are using that, doesn't it look at the volume size of your C drive and complain if it's not the right size? IE: you are trying to re-partition your C drive and this may cause problems if the recovery console doesn't like your new C drive.

- If you aren't using a recovery console and have the cd/dvd or something, could you try wiping the partition another way? Use a linux disc or something like that.